of the OECTs were evaluated by using three-terminal electrical measurements.
The integrated measurement system included two source meters (Keysight
B1500A and Agilent B2912A) and a switching matrix (Agilent E5250A),
all managed on a personal computer using custom LabVIEW software.
The electrical signals of the as-prepared OECT device were recorded
in 0.1 M PBS (pH 7.4) buffer with a Ag/AgCl wire serving as the gate
electrode. The drain current (Id) was
obtained by applying source-gate voltages (Vg: from 0 to +0.8 V) at a fixed source-drain potential (Vd = −0.1 V). Transconductance (gm) curves were obtained by deriving the transfer
curves and definition given in
Following each immobilization
step, the devices underwent thorough rinsing in water and subsequent
testing in the electrolyte. Transfer characteristics were recorded
with Vg = −0.8 to 1 V and Vd = 0.1 V. FTIR spectroscopy was conducted using
the ATR-FTIR, Jason, FT/IR-6700, Tokyo, Japan. Electrochemical impedance
spectroscopy and cyclic voltammetry measurements were performed with
a three-electrode system utilizing an Autolab potentiostat (PGSTAT128N,
ECO CHEMIE BV, Netherlands), with platinum as the counter electrode
and Ag/AgCl as the reference electrode. The electrolyte used was 0.1
M PBS (pH 7.4). A SEM was used to observe the surface morphologies
of the
of the modified surfaces were dried. To confirm the attachment of
streptavidin to
with streptavidin-cy5 for 1 h and observed under a confocal fluorescence
microscope.